LCI drive systems are conventionally used for operating various electrical machines such as heavy duty turbomachines, electrical motors, compressors, pumps, and so forth. Conventionally, a LCI provides a current source to an electrical machine through the use of silicon controlled rectifiers (SCRs) which transform, based on the current operation of the electrical machine, direct current (DC) to multiphase alternating current (AC) for supplying the AC to the electrical machine. LCI drive systems are designed for operating electrical machines in both starting operation mode, also known as a force commutated mode, and a “normal” operation mode, also known as a self commutated mode. Variable frequency AC power allows starting electrical machines without auxiliary equipment.
Typically, LCI drive systems are designed for specific synchronous electrical machines and, especially, for those machines performing heavy duty tasks. Such drive systems have high power ratings and involve utilizing high operating voltages. To decrease the operating voltages, conventional systems use at least six or nine phase synchronous electrical motors, with each of three phases coupled to a separate lower power LCI drive. Such systems are very complex in nature because multiple LCI drives need a complex controlling scheme, synchronizing scheme, complex wiring, the need to use bypass switching to allow for operating at low frequencies, and so forth.